Electric vehicles typically have many large battery modules connected in series or in parallel to form a single large battery system. Electrical characteristics of these electric vehicle battery systems, such as temperature and voltage, conventionally are monitored using thermocouples and metal wires interconnected to a large central multiplexing unit. Interconnecting with metal wires the many components of these systems proves disadvantageous because of the increased risk of electrical shorts that results from a high degree of wiring complexity. In fact, containment of as few conductors as possible in the high-voltage battery compartment is desirable. Interconnection of a large number of electrical components with metal wires so as to increase system weight and volume also proves disadvantageous in electrical vehicle applications where the size of the battery system has been expanded thereby creating tight packaging constraints.
Therefore, to reduce the complexity of the central multiplexing equipment and the risk of electrical shorts, and to improve the reliability and manufacturability of the battery monitoring system, a self-contained battery monitoring system for electric vehicles is desired having individual monitors attached to each series or parallel-connected battery module in the system and interconnected with optical fibers to a central computer.